Methods are known from WO 03/045694 A1 and WO 03/045695 A1 in which a smooth and easy flow of a printing ink on a rotating component of a printing group, which is working together with the printing ink, is kept substantially constant within a temperature range between 22° C. and 50° C. by controlling the temperature of the rotating component. The smooth and easy flow of the printing ink is a function of the temperature on the outer surface of the rotating component and of its production speed. These methods are used particularly in connection with a waterless printing group, and preferably in a printing group for newspaper printing.
EP 0 652 104 A1 discloses a printing group for use in waterless offset printing, and having a control unit with several controllers which controllers, for preventing the build-up of printing ink on a transfer cylinder of the printing group, control respective control valves for regulating the amount of coolant, such as, for example, water, which is supplied to the respective cylinders. The amount of coolant is supplied at a rate which is a function of the deviation from a predetermined value of a temperature detected at the transfer cylinder or at a forme cylinder of the printing group associated with the forme cylinder, at or an ink distribution cylinder of an inking unit which is associated with the forme cylinder, by the use of a thermal sensor. The regulation of the amount of coolant is intended to make it possible to keep a temperature of a printing forme on the forme cylinder within a temperature range of 28° C. to 30°, for example, during the course of printing. The intent is to also keep the temperature of the transfer cylinder between approximately 34° C. and 35° C. and to keep the temperature of the inking unit between 25° C. and 27° C. It is also possible to preheat the printing group, through the supply of the coolant quantity, thus making it possible to prevent pulling of the printing ink at the start of printing, and to also limit the collection of paper particles in the inking unit.
The course of the temperature of the coolant, for pre-heating the printing group, can be regulated in accordance with a temperature/time curve which is stored, for example, in a memory that may be housed in the control device.
A temperature-regulating device in a printing group is known from DE 197 36 339 A1/B4. The Theological properties of the printing ink, such as its viscosity or tackiness, for example, can be influenced through temperature regulation. The associated printing press, with a forme cylinder, has a short inking unit which is equipped with an ink fountain, a screen roller and an ink-application roller. The temperature-regulating device can regulate the temperature of at least one of the inking unit rollers or of the forme cylinder. The temperature regulation takes place by either cooling or heating, either from the direction of the outer surface of the ink unit rollers or of the forme cylinder, or from the interior of the ink unit rollers or the forme cylinder. The ink fountain, and in particular the doctor blade, can additionally be temperature-regulated, for removing excess printing ink from the screen roller. The amount of printing ink which is transferred to the forme cylinder can be regulated by the use of a control circuit. An optical density measured on the material to be imprinted is used as the signal value, by the use of which signal value, the control device that is associated with the temperature-regulating devices controls the temperature of the latter.
A method for controlling the amount of a medium, and in particular the amount of ink or lacquer, which is transferred by a screen roller of a printing press to a roller in contact with the screen roller, by influencing a difference in circumferential speeds between the screen roller and roller is known from DE 101 43 827 A1. The difference in circumferential speeds is controlled, as a function of the printing speed of the printing press, in such a way that the imprinted medium density is constant, or remains approximately constant, at least within a wide printing speed range. It is possible to raise the imprinted medium density by increasing the screen roller temperature, or to lower the imprinted medium density by reducing the screen roller temperature. In this case, the imprinted medium density is the optical density of a print image which is transferred to the material to be imprinted and not the material density of the printing medium.
In DE 44 31 188 A1, a printing forme of a printing group for use in waterless offset printing is cooled to approximately 28 to 30° C. This cooling is accomplished by the use of a cooling device.
A printing device with a counter-pressure cylinder and with an ink-application unit and having at least one roller for use in transferring printing ink to a substrate backing is known from DE 41 08 883 A1. The substrate backing passes between the counter-pressure cylinder and the ink-application unit. The counter-pressure cylinder and/or the ink-application unit are divided, in the axial direction, into several thermal zones. These thermal zones have individually controllable temperature-regulation devices for use in changing the viscosity of the printing ink in each of the respective zones.
It is known from DE 39 04 854 C1 that the rotation speeds of the cylinders of the printing group, of the inking unit, and of the dampening unit all influences the inking unit temperature.
DE-OS 19 53 590 discloses a printing group with an inking unit and with a dampening unit, whose temperature can be regulated by the use of a temperature-regulating device. Prior to the start of a printing process, a desired value of the temperature, as a function of influencing variables such as the printing speed, can be determined by the use of test printings or can be set by the use of tables. An advantageous upper limit of the temperature of the printing ink is set forth to be the room temperature.
Details regarding the tackiness of printing ink are explained in ISO 12634, dated Nov. 15, 1996. Details regarding viscosity of a printing ink, as well as details regarding methods for measuring printing ink viscosity, are explained in ISO 12644, dated Dec. 01, 1996.